1. Field of the Invention
The present invention relates to a method of controlling a device for feeding a sheet-like member reciprocally with a belt engaging a rotary actuator and also feeding the sheet-like member in an auxiliary scanning direction when the sheet-like member is scanned with a light beam.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor is used as a stimulable phosphor sheet.
The above known system includes an image information reading apparatus which comprises a loading unit for accommodating a cassette which stores a stimulable phosphor sheet with the radiation image information of a subject being recorded thereon, a reading unit for photoelectrically reading the recorded radiation image information carried on the stimulable phosphor sheet that has been removed from the cassette, and an erasing unit for erasing residual radiation image information remaining on the stimulable phosphor sheet.
The system also includes an image information reproducing apparatus for recording the radiation image information read from the stimulable phosphor sheet on a photographic film (sheet-like member). The image information reproducing apparatus comprises a loading unit for accommodating a container such as a cassette, a magazine, or the like which stores a photographic film, and a recording unit (scanning unit) for recording radiation image information on the photographic film.
Each of the reading unit and the recording unit incorporates an auxiliary scanning feeding device for feeding the sheet-like member in an auxiliary scanning direction when a laser beam as stimulating light or recording light is applied to the sheet-like member in a main scanning direction which is substantially perpendicular to the auxiliary scanning direction.
FIG. 5 of the accompanying drawings shows in plan a general auxiliary scanning feeding device 1. As shown in FIG. 5, the auxiliary scanning feeding device 1 has two feed rollers pairs 2a, 2b spaced a certain distance from each other. A belt and pulley mechanism 5 is mounted on a rotatable shaft 4a of a drive roller 3a of the feed roller pair 2a and a rotatable shaft 4b of a drive roller 3b of the feed roller pair 2b. A driven pulley 6 is also fixedly mounted on the rotatable shaft 4a. An endless belt 9 is trained around the driven pulley 6 and a drive pulley 8 that is fixedly mounted on the drive shaft of a motor 7.
When the motor 7 is energized to rotate the drive shaft thereof in one direction, the feed roller pairs 2a, 2b are rotated in one direction synchronously with each other. A sheet-like member, e.g., a stimulable phosphor sheet S, is fed in an auxiliary scanning direction indicated by the arrow A by the feed roller pairs 2a, 2b while stimulating light (not shown) is being applied to the stimulable phosphor sheet S. Upon exposure to the stimulating light, the stimulable phosphor sheet S emits light representing radiation image information recorded thereon, which is photoelectrically read. Thereafter, the motor 7 is energized to rotate the drive shaft thereon in the opposite direction, causing the feed roller pairs 2a, 2b to feed the stimulable phosphor sheet S in the direction indicated by the arrow B until the stimulable phosphor sheet S is discharged out of the auxiliary scanning feeding device 1.
The auxiliary scanning feeding device 1 employs the belt 9 as a transmitting means for transmitting the rotational power of the motor 7 to the feed roller pairs 2a, 2b. The belt 9 may possibly slide or sway sideways in different directions when the stimulable phosphor sheet S is fed forward in the direction indicated by the arrow A and backward in the direction indicated by the arrow B. For example, when the stimulable phosphor sheet S is fed forward in the direction indicated by the arrow A, the belt 9 may slide or sway sideways in the direction indicated by the arrow C across the driven pulley 6, and when the stimulable phosphor sheet S is fed backward in the direction indicated by the arrow B, the belt 9 may slide or sway sideways in the direction indicated by the arrow D across the driven pulley 6.
Therefore, even though the stimulable phosphor sheet S needs to be fed highly accurately in the auxiliary scanning direction indicated by the arrow A, the drive rollers 3a, 3b of the feed roller pairs 2a, 2b tend to suffer rotation irregularities due to the lateral sliding of the belt 9 on the driven pulley 6. When the drive rollers 3a, 3b are subjected to rotation irregularities, the image read from the stimulable phosphor sheet S also suffers image irregularities or distortions, and hence the radiation image information recorded on the stimulable phosphor sheet S cannot be read highly accurately.
It is a major object of the present invention to provide a method of controlling a device for feeding a sheet-like member in an auxiliary scanning direction by canceling out, in advance, the effect of a lateral sliding of a belt engaging a rotary actuator according to a simple control process, for thereby feeding the sheet-like member highly accurately and smoothly in the auxiliary scanning direction.
According to the present invention, a rotary actuator is rotated in a first direction to rotate a belt to feed a sheet-like member in another direction. Before the sheet-like member is scanned by a light beam, the rotary actuator is rotated in a second direction which is opposite to the first direction to rotate the belt by a predetermined length. Thereafter, the rotary actuator is rotated in the second direction to rotate the belt to feed the sheet-like member in an auxiliary scanning direction while scanning the sheet-like member with the light beam.
Even if the belt is slid or swayed sideways when the rotary actuator is rotated in the first direction, before the sheet-like member is scanned by the light beam, the rotary actuator is rotated in the second direction to allow the belt to slide or away sideways in an opposite direction, thus positionally stabilizing the belt. When the sheet-like member is scanned by the light beam, the rotary actuator is rotated in the second direction to rotate the belt in a stable position, thereby making it possible to feed the sheet-like member highly accurately in the auxiliary scanning direction. The sheet-like member can thus be scanned highly accurately. Since the belt which engages the rotary actuator can be used, the entire device for feeding the sheet-like member in the auxiliary scanning direction is easily simplified in structure.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.